Demonstrate that Water is Diamagnetic

This photograph shows the slight downward deflection of
the surface of the water above a strong rare-earth magnet. This is
my version of the setup described by Conery and others in The Physics
Teacher (v. 41, February
2003). It was not easy to get the lighting
angle "just right" so that the indentation about the magnet
would be visible.

Materials:

Rare earth magnet

Plastic cat food lid

Food coloring

I added just enough water to cover the bottom of the lid and enough
food color so that the reflection would be from the upper surface.
Then the lid sits on top of the magnet.

This is a nice setup for occasional repeated use because the when the
water evaporates the coloring remains in the lid and can be reused with
the addition of water.

I tried viewing the reflection of many different lights and
the only one that would work as shows was my kitchen ceiling light.
Even so, the angle of view was critical in order to "see" the
very slight depression in the water's surface.

See Bill's message below for another way to detect the depression in the
water.

When I heard about this, I went and found a sunbeam in the kitchen and

placed a bowl of water there. The water reflected a spot of light
uponthe ceiling. (I knew from "dishwashing
experiments" that such a lightspot is incredibly
sensitive to tiny distortions of the surface, such asblowing
upon it.) Sure enough, placing a magnet under the water caused abright
spot to form in the otherwise uniform reflection. This indicatesthat
the magnet forms a depression. Hey, maybe with the right shape ofmagnet
stack we could create a paraboloid with very long focal length.